CAIRO —
Shootings in front of a military facility Monday in Cairo have left dozens of people dead and dozens more wounded, according to an Egyptian health ministry official. Reports about who ignited the shoot-out are conflicting, with Muslim Brotherhood supporters accusing the army, and army officials insisting it was a “terrorist attack.”

Witnesses said the shootings began just before the end of dawn prayers Monday. The Muslim Brotherhood demonstrators and the Egyptian Army each accused the other side of starting the violence.

The Health Ministry said Monday at least 51 people were killed and hundreds more wounded in the early flare-up near Republican Guard headquarters. Military officials said one soldier was among the dead and several more were in critical condition.

Pro-Muslim Brotherhood doctors at a field clinic held a news conference in which they claimed the army had used excessive force. Clinic doctors said they treated more than 400 serious wounds, including 150 gunshot wounds.

Al-Jazeera television showed amateur video of a half dozen people it said were peaceful protesters shot by the army. Egyptian state TV also showed video of assailants pelting soldiers with stones and chunks of concrete as gunshots are heard in the background.

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Muslim Brotherhood spokesmen called the shootings a “massacre,” while an army statement insisted a “terrorist attack” had taken place.

An injured Egyptian soldier, Mohamad Ibraheem described what he experienced.

He said he and other soldiers were there to ensure the safety of the people, but came under attack with gunfire, firebombs and bricks. He said many of his colleagues were hit.

It was not immediately possible to reconcile the conflicting accounts.

Egyptian interim President Adly Mansour was reported to have appointed a judicial committee to investigate Monday's shootings. A presidential statement expressed “deep regret” for the violence, but went on to say the shootings took place during an attempt to storm Republican Guard headquarters.

Amid the accusations, Al-Arabiya TV showed a video of Islamist cleric Safwat Hijazi, who supports ousted President Mohamed Morsi, insisting that “all means” would be used to “free Mr. Morsi” from army custody.

Republican Guard Headquarters, Cairo, Egypt

During the February 2011 revolution which toppled veteran strongman Hosni Mubarak, Islamist militants freed Morsi and other top Muslim Brotherhood leaders from a Sinai prison, and attacked other Egyptian prisons as well.

As reports of Monday's shootings spread, several Islamist groups announced they would not participate in an interim government that was being formed by Mansour. The Salafi Nour Party called for President Morsi to be reinstated, as did Islamist leader and former presidential candidate Abdel Moneim Aboul Foutouh.

A statement by the Muslim Brotherhood called for Egyptians to “rebel against those who stole their revolution from them.” Thousands of Brotherhood supporters continued to protest in front of Cairo's Rouba Adawiya mosque as army troops watched from a distance.

Top opposition leader Mohamed ElBaradei called for the “immediate formation” of an interim government, in the wake of the violence. ElBaradei had been the initial favorite to head that government, before meeting resistance from the Nour Party.